code: def activate_zoom(self):
      self.width, self.height = self.size
      gloo.set_viewport(0, 0, *self.physical_size)
      self.program_v["u_screen"] = self.physical_size
  
file_path: vispy/examples/demo/gloo/voronoi.py
imports: import numpy
  from vispy import app
  from vispy import gloo
label_desc: Use image node_id 4 for calling the Canvas obj's underlying member method code with example usage: obj.activate_zoom() without return types